This invention relates to a topsheet for a body fluids absorbent article such as a sanitary napkin or a disposable diaper and also to a method of making this topsheet.
It is well known to make a nonwoven fabric by subjecting a web of thermoplastic synthetic resin staple fibers each having a length of 20.about.70 mm to water jet streams of high pressure so that the fibers may be mechanically entangled and simultaneously liquid-permeable openings may be formed. The nonwoven fabric obtained in this manner can be used as the liquid-permeable topsheet of a sanitary napkin, a disposable diaper or the like. By such a method, the staple fibers tend to extend in parallel one to another along the direction in which the web travels. Consequently, the staple fibers extend closely in parallel one to another particularly along peripheral edges of the respective openings. These staple fibers thereby define correspondingly clear contours of the respective openings so far as these openings are oval openings each having a major axis extending along the direction in which the web travels and a minor axis extending orthogonally to the direction.
FIG. 8 shows an example of the porous nonwoven fabric 101 obtained by the above-mentioned method. As shown, the nonwoven fabric is formed with a plurality of oval openings 102 each having a major axis A--A extending in one direction and a minor axis B--B extending in the direction orthogonal to the major axis A--A. It is now assumed that the nonwoven fabric 101 is pulled, for example, in the proximity of one (102a) of the openings 102 in the direction of the major axis A--A. A dimension of this opening 102a as measured in the direction of its major axis A--A is enlarged while a dimension thereof in the direction of its minor axis B--B is reduced, with a result that this opening 102a may be deformed narrower as indicated by imaginary lines. If many of the openings 102 are deformed narrower like the opening 102a with their dimensions in the direction of their minor axes B--B extremely reduced, the nonwoven fabric 101 can not satisfy its desired function. This is for the reason that the openings 102 can no more smoothly guide body fluids and a time during which the body fluids stay on the topsheet, creating a discomfortable feeling of wetness against a wearer of the article.